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Re: [PSUBS-MAILIST] Acrylic Molds

Hi guys, just got in, I've been out exploring in the boonies around here.

I'll put together a drawing of the backwoods acrylic oven soon and post a link.

 The basics of it are simple, picture a shoe box the size you need without the lid, line it with
aluminum foil using double faced tape around the edges then stapled through the tape and foil.
 Now in the side cut an inspection hole about  1/4 of the way down and centered, 6" X 10" and
cover it with 1/4" plate glass.
 At the bottom of the 2 ends cut several small breathing holes and a heater access door.
 Place your heater in the center of the box and build a metal rack that is about 3" higher than the
top of your propane barbecue (without the legs) or propane heater, and place a sheet of 1/8" aluminum
or sheet metal, (somewhat larger than your heat source) on the rack to evenly distribute the heat throughout the box.
 Around the top edge on the outside of the box attach a framework of 1x2 or or angle iron (bed frames work nicely)
to clamp your former sheet and acrylic to. And finally, mount an oven thermometer on the wall across from
your inspection window.

 Now here is where the different techniques determine which way you need to go. For AquaNuts we really only
have two choices ambient or 1atm. If it's non structural you can blow it, if it's structural it should be draped which
will require a male mold, coffin like handles clamped along the sides of the acrylic and a few strong helpers.

To blow mold requires a box top of sturdy plywood with a air fitting centered and countersunk flush on the bottom
side and fitted with a shut off valve and quick connector at the top side. Around the bottom border attach a gasket of
weather stripping.
Now with another sheet of plywood cut out the shape you want to make but make it a bit larger than the planned finished
part. Paint the top side around the cut out with polyester resin or primer/ surfacer about 3-6" wide and sand smooth.
Then polish with 2 or 3 coats of a good automotive car wax.

Your acrylic sheet will now be sandwiched between the former sheet and the top and secured firmly with either clamps
or preferably bolts and wing nuts.

Now light up the ol barbecue and place your wood and acrylic sandwich on top of your box and secure it to the flange at
the top of the box and you're cookin!

At around 175-300º F (depending on the thickness & particular properties of the acrylic used) the plastic begins to sag,
this is where you begin to add a little air pressure (on large canopies you can draw your projected profile with a permanent
marker on the back wall of the box as a reference), slowly increase the air pressure until the plastic is just slightly larger
than spec and turn off the heat while maintaining your pressure and let slowly cool.

That's about it.

To make a simple bend you just need a strip heater available at most places that sell acrylic, solvents and tools.
Or if you're really good and quick you can use a heat gun,,,,, I'm not!

I hope this helped, I'm off to dream about my next baking soda and vinegar powered Psub! Night all.

Doc

Reference;
http://www.plaskolite.com/fabguide/pg11.pdf
http://www.chemcastacrylic.com/technical/mx4b.htm
www.tapplastics.com/plastics/ plasticsinfo/hi-acrylic.html
www.sdplastics.com/acrylit1.html
www.sunlight-tech.com/acrylic_tech_data.html
www.manufacturing.net/esec/Article_85859.htm


DJACKSON99@aol.com wrote:

> Doc
>
> I need to bend a 35 degree turn in a 1 inch thick sheet of Acrylic that is 4 feet by 4 feet. I found a couple of helpful web sites (below) but I'd really like to see a photo and description of your oven.
>
> http://www.chemcastacrylic.com/technical/techinfo.htm
> http://www.bayplastics.co.uk/product%20guide/Altuglas-guidenavbar/prod-altuglass-tech(bending).htm
>
> Please keep it online.
>
> Thanks
> Doug
>
> >Mark;
> > I've done considerable research and testing on different ways to form
> > acrylic in the barn, from gravity to blow molding to drape forming of
> > up to 1 inch thick over a male fiberglass mold. For blow molding or
> > gravity forming, you can coat your separation points (ring) with a
> > layer of epoxy resin or gelcoat and a thin coat of car wax. You can
> > build a 4'X8' forming oven out of plywood or chip board, aluminum foil
> > , a piece of 1/4" plate glass and a propane barbecue!
> >
> >Doc